This type represents a DOM element's attribute as an object. In most DOM methods, you will probably directly retrieve the attribute as a string (e.g., Element.getAttribute()
, but certain functions (e.g., Element.getAttributeNode()
) or means of iterating give Attr types.

Warning: In DOM Core 1, 2 and 3, Attr inherited from Node. This is no longer the case in DOM4. In order to bring the implementation of Attr up to specification, work is underway to change it to no longer inherit from Node
. You should not be using any Node
properties or methods on Attr objects. Starting in Gecko 7.0 (Firefox 7.0 / Thunderbird 7.0 / SeaMonkey 2.4)
, the ones that are going to be removed output warning messages to the console. You should revise your code accordingly. See Deprecated properties and methods for a complete list.

Indicates whether the attribute is an "ID attribute". An "ID attribute" being an attribute which value is expected to be unique across a DOM Document. In HTML DOM, "id" is the only ID attribute, but XML documents could define others. Whether or not an attribute is unique is often determined by a DTD or other schema description.